The present invention relates generally to bicycles and, more particularly, to air shock assemblies that are constructed to facilitate adjustable controlled movement between movable members of a bicycle, such as a frame and a wheel assembly.
The primary structural component of a conventional two-wheel bicycle is the frame. On a conventional road bicycle, the frame is typically constructed from a set of tubular members assembled together to form the frame. For many bicycles, the frame is constructed from members commonly referred to as the top tube, down tube, seat tube, seat stays and chain stays, and those members are joined together at intersections commonly referred to as the head tube, seat post, bottom bracket and rear dropout. The top tube usually extends from the head tube rearward to the seat tube. The head tube, sometimes referred to as the neck, is a short tubular structural member at the upper forward portion of the bicycle which supports the handlebar and front steering fork, which has the front wheel on it. The down tube usually extends downwardly and rearward from the head tube to the bottom bracket, the bottom bracket usually comprising a cylindrical member for supporting the pedals and chain drive mechanism which powers the bicycle. The seat tube usually extends from the bottom bracket upwardly to where it is joined to the rear end of the top tube. The seat tube also usually functions to telescopically receive a seat post for supporting a seat or saddle for the bicycle rider to sit on.
The chain stays normally extend rearward from the bottom bracket. The seat stays normally extend downwardly and rearward from the top of the seat tube. The chain stays and seat stays are normally joined together with a rear dropout for supporting the rear axle of the rear wheel. The front wheel assembly is commonly mounted between a pair of forks that are pivotably connected to the frame proximate the head tube. The foregoing description represents the construction of a conventional bicycle frame which does not possess a suspension having any shock absorbing characteristics.
The increased popularity in recent years of off-road cycling, particularly on fairly rough terrain and cross-country, as well as an interest in reducing discomfort associated with rougher road riding, has made shock absorbing systems a desirable attribute in biking system. A bicycle with a properly designed suspension system is capable of traveling over extremely bumpy, uneven terrain and up or down very steep inclines. Suspension bicycles are less punishing, reduce fatigue, reduce the likelihood of rider injury, and are much more comfortable to ride. For off-road cycling in particular, a suspension system greatly increases the rider's ability to control the bicycle because the wheels remain in contact with the ground as they ride over rocks and bumps in the terrain instead of being bounced into the air as occurs on conventional non-suspension bicycles. Bicycles equipped with suspension systems has dramatically increased over the last several years. In fact, many bicycles are now fully suspended, meaning that the bicycle has both a front and rear wheel suspension systems. Front suspensions were the first to become popular. Designed to remove the pounding to the bicycle front end, the front suspension is simpler to implement than a rear suspension. A front suspension fork is easy to retrofit onto an older model bicycle whereas a rear suspension will increase traction and assist in cornering and balance the ride.
During cycling, as the bicycle moves along a desired path, discontinuities of the terrain are communicated to the assembly of the bicycle and ultimately to the rider. Although such discontinuities are generally negligible for cyclists operating on paved surfaces, riders venturing from the beaten path frequently encounter such terrain. With the proliferation of mountain biking, many riders seek the more treacherous trail. Technology has developed to assist such adventurous riders in conquering the road less traveled. Wheel suspension systems are one such feature.
Even though suspension features have proliferated in bicycle constructions, the performance of the suspension as well as the structure of the bicycle are often limited to or must be tailored to cooperate with the structure and operation of the shock. Commonly, both ends of the shock are secured to the bicycle between movable frame members where movement is intended to be arrested, dampened, or otherwise altered. The shock is often connected between a portion of the frame and structure proximate an axle of an associated wheel to provide a desired travel distance and/or resistance to the relative displacement of the structures secured to the generally opposite ends of the shock. The incorporation of the shock member with the bicycle and the internal operation of the shock assembly generally determine the motion performance of the suspension.
Altering the suspension performance of a particular bicycle can require changing the entire shock, changing components of the shock, altering the physical arrangement of the shock relative to the bicycle, and/or manipulating an operating pressure of the shock assembly. Understandably, the desired operation of a shock assembly can vary due to a number of characteristics including terrain conditions, rider suspension performance preference, rider size and weight, and/or bicycle geometry.
Air or fluid shock assemblies generally provide the most convenient means for adjusting operation of the shock assembly. The performance of many air shock assemblies can be adjusted by manipulating the pressure of an air or fluid chamber. However, the adjustability of such systems is commonly limited as a function of the properties of the fluid itself and/or the geometric constraints of the shock assembly. To increase the adjustability or the operating range of such systems, many fluid shock assemblies are provided with fluid reservoirs or chambers that are external to the generally linear body of the shock assembly. Such configurations require greater spatial consideration for integrating the shock assembly with the underlying bicycle. Such configurations also complicate the construction of the shock assembly by requiring the formation of various fluid communication paths for communicating fluid into and out of the shock leg.
Although other shock assemblies provide air or fluid chambers that remain fully internal to the generally linear body of the shock assembly, such assemblies present other shortcomings. Commonly, such systems include a fluid chamber that is formed by one of the stanchion tube or the leg or slider tube. A piston telescopically cooperates with the respective tube and compresses the fluid when the shock assembly is subjected to a compression load. Commonly, such systems also include a floating piston that also cooperates with the respective tube to accommodate changes to the fluid chamber. Such configurations create undesirable dependencies between the size of the fluid chamber, the size of the stanchion tube, and the size of the pistons to satisfy given geometric and suspension performance criteria.
In an attempt to increase the application of a given shock assembly, others have generated shock assemblies that are constructed to accommodate one of a number of coil springs. Shock performance can be achieved simply by replacing a coil spring contained within the shock assembly. Unfortunately, such systems require manufactures provide a number of springs that are configured to specific shock geometries. Such a requirement increases operating costs for manufacturers and complicates distribution by requiring providing of a number of coil springs for given shock geometries and desired suspension performance.
Shocks with interchangeable coil springs are also adjustable in less than a desirable manner. Commonly, such adjustment requires at least partial disassembly of the shock assembly. Such disassembly commonly requires specialized tools and knowledge. It is therefore impractical to reconfigure the performance of such shock assemblies under in-field conditions.
If a rider has multiple bicycles, as many competitive riders do, acquiring the components and knowhow to alter the performance of the suspension of a number of bicycles can be particularly expensive. With respect to shock manufacturing, as the structure of bicycle suspension features changes, shocks must be restructured to cooperate with the new bicycle structure. Shock design, construction, and assembly can become particularly costly in those instances where a variety of different shocks or coil springs having different shock performance characteristics must be provided for one particular bicycle to satisfy individual rider preferences and/or preferences associated with varied riding conditions. Satisfying individual rider preferences across the various product platforms of various bicycle manufactures requires providing uncountable specific shock constructions.
Therefore, there is a need for a shock system that can be configured to provide a conveniently tunable suspension performance. There is a further need for a shock system that can provide a variety of shock performances in a manner that at least partly decouples the dependency of the performance of the shock assembly from the physical geometry of the shock assembly. There is a further need for a bicycle shock system that can be quickly and efficiently tuned by the rider to provide a desired suspension performance specific to particular conditions.